In conventional capacitor on plug (COP) devices, contact plugs are often used as vertical interconnects between metal lines in multilevel interconnect schemes. During processing of a contact window (CW) hole opening using an oxide reactive ion etch (RIE), oxygen forms in the Tetraethyl Orthosilicate (TEOS) hardmask covering the capacitor. An iridium (Ir) based barrier is often positioned between a bottom electrode (BE) and the TEOS substrate to block oxygen from causing damage when it diffuses to the plug. However, TEOS residues of the etching process (“fences”) can form during RIE processing of the bottom electrode. These fences allow the oxygen to diffuse from the TEOS hardmask to the plugs during the contact window hole RIE processing. This oxygen reacts with the material of the plug, for example poly silicon or Tungsten, causing functional damage to the plug structure, in particular causing contact degradation.
One way to avoid this plug oxidisation problem is to make the bottom electrode RIE process such that no oxygen-diffusion-allowing fences are formed. However, this is difficult to achieve in typical processes where the hardmask covering the bottom electrode during bottom electrode RIE processing has a steep taper angle.
Another way to avoid the plug oxidization problem is to remove the TEOS fences after they were formed. However, this is a difficult and complex process.
In view of the foregoing problems with conventional processes and devices, a need exists for a method for inhibiting oxidation of the plug during the manufacture of a capacitor.